The effect could be irreversible for tens of thousands of years, the academies said. They urged countries attending U.N. climate negotiations in Bonn, Germany, this week to cut the world's CO2 emissions at least 50 percent below 1990 levels by 2050, with additional cuts after that.

Without such action, the consequences will be stark, the academies said. "At current emission rates models suggest that all coral reefs and polar ecosystems will be severely affected by 2050 or potentially even earlier," they wrote.

Some climate models suggest that, at current CO2 emissions levels, 80 percent of Arctic waters could prove corrosive to clams, pteropods and other species at the base of the polar food chain by 2060, the new statement said.

If the level of carbon dioxide in the atmosphere reaches 550 parts per million -- compared with the current 387 ppm level -- "coral reefs may be dissolving globally."

For humans, a major impact would likely be a resulting decline in the world's fishery production.

Scientists have already begun to document how rising CO2 emissions are driving changes in the world's oceans. Since the 17th century, the seas have absorbed about a third of human-caused carbon dioxide emissions. That has resulted in water 30 percent more acidic than it was before factories, cars, planes and other fossil fuel-burning machines became widespread.

Researchers believe that chemical shift will pose a major problem for shellfish, corals and other marine life that grow hard shells made of a chalky mineral called calcium carbonate. At lower levels of acidity, it can become harder for shelled species to grow. If ocean water becomes too acidic, it can begin dissolving those shells, sometimes faster than the creatures can rebuild them.

Martin Rees, president of the U.K. Royal Society, said ocean acidification could lead to an "underwater catastrophe" without sharp cuts to the world's CO2 emissions.

"The effects will be seen worldwide, threatening food security, reducing coastal protection and damaging the local economies that may be least able to tolerate it. Copenhagen must address this real and serious threat," Rees said in a statement, referring to international climate talks scheduled to take place in the Danish capital in December.